324
FXUS66 KPQR 131818
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1018 AM PST Thu Nov 13 2025

Updated aviation discussion.

.SYNOPSIS...Low pressure offshore will maintain rain across
northwest Oregon and southwest Washington today. A showery
pattern continues through the weekend with seasonable
temperatures. Cooler temperatures early next week will bring
snow levels down and return chances for snow through the Cascade
passes.

&&

.SHORT TERM...Now through Saturday night...A lifting warm front
associated with a low pressure system centered offshore of
northern California is spreading rain from south to north across
our area. Ensemble guidance remains in agreement that this low
will progress inland toward southern Oregon and northern
California. Therefore, the majority of impacts from this system
is favored further south of our area. However, we`ll still get a
decent amount of rain out of this system. Over the next 24
hours (4 AM Thursday to 4 AM Friday), chances for 0.50" of rain
or greater is around 25-35% across the Willamette Valley and
Portland-Vancouver Metro Area, 40-60% across the Lower Columbia,
Cowlitz Valley, and Hood River Valley, and 60-80% along the
coast, Coast Range, Willapa Hills, and Cascades. The 90th
percentile (10% chance), shows around 1.2-2" along the coast
and Coast Range, and around 0.70-0.90" inland. Snow will not be
a concern today as the warmer air ushered in from the south
from this low will maintain snow levels well-above the passes
(9000 ft+).

Winds are also non-impactful today, but easterly winds remain
breezy through the Columbia River Gorge and eastern Portland
Metro through this afternoon with gusts of 20-25 mph. Easterly
winds are also present along the coast with similar wind gusts.
Pressure gradients between Troutdale and The Dalles (KTTD-KDLS)
remain around -3 to -4 mb this morning, but will gradually ease
this afternoon, thus weakening easterly winds. Winds will
generally turn more southerly/southwesterly this afternoon as a
weak occluded front moves northward from the low, breeziest
along the coast with gusts up to 20 mph. Elsewhere, winds remain
light.

Rain will persist through Friday as the low shifts southward.
Another frontal system will swing through British Columbia and
far northwest Washington Friday evening into Saturday,
maintaining >60% chances for precipitation along the coast and
southwest Washington. Warm air will linger over the area but a
brief area of cooler air settles in. This airmass has warmed
though over the last few forecast cycles so, while snow was
previously expected at pass level, that is no longer the case.
Snow levels will fall to 5500-6000 ft, so impactful snow is no
longer expected through the Cascade passes. Chances for
precipitation fall (but remain non-zero) especially inland by
Saturday evening as the region is in between systems and weak
ridging builds over the region. Overall, expect pretty typical
fall weather these next few days.      -10/27

&&

.LONG TERM...Sunday through Wednesday...Conditions will remain
showery on Saturday night into Sunday morning but then
conditions will quickly shift Sunday night. Another cold air
wrapped low aloft will move over British Columbia extending a
long wave trough over the region. This trough has a band of
enhanced vorticity advection, moisture, and potentially breezy
winds. Accumulating rain will be less on Sunday but will ramp up
through Monday as the trough intensifies and a closed low forms
at the base. This forming low will wrap even more cold air
behind it causing temperatures to drop. At 850 mb, temperatures
will reach freezing by late Monday morning and continue to lower
through late Tuesday night. At the surface this trend will be
coupled causing snow levels to fall to around 3500 ft. With this
current pattern there will likely be pass-level snow. However,
if the low advects further north then the colder air may not
filter in as far south and thus we would miss enough of the cold
effect for snow to form. Current NBM guidance suggests a 20-30%
chance for 6 inches of snow or greater from 4 AM Sunday to 4 AM
Tuesday through Highway 26 near Government Camp and the Santiam
and Willamette Passes.

While snow in the passes is one component to look at, surface
temperatures too will cool Monday night into Tuesday morning.
While freezing temperatures (32 deg F or 0 deg C) are not
expected to be widespread in the lowlands, the chances are non-
zero. In the southern Willamette Valley and outskirts of the
central Willamette Valley, there is around a 30-50% chance of
freezing temperatures, in the Portland-Vancouver Metro there is
a 5-15% chance, and a less than a 5% chance along the coast. In
the Upper Hood River Valley these chances are 60-90%, with the
highest chances near Parkdale. Similar chances are observed
through Wednesday morning. Heading into mid-week, there is
uncertainty among ensembles on the overall weather pattern.
                                                     -10/27

&&

.AVIATION...At 18z Thu, the band of rain that moved north through
the region early this morning is moving into central WA and will be
out of southern WA by 19-20z Thu. Widespread VFR conditions have
returned behind this precipitation except for a portion of the
southern Willamette Valley that is observing MVFR/IFR CIGS or VIS
due to stratus. This stratus is expected to clear by 19-21z Thu.
Another round of scattered showers is beginning to push into Lane
County from the south and will continue spreading across the region
through the day. There`s a 30-60% chance for MVFR CIGs with this
precipitation through 00z Fri at terminals west of the Cascades,
with higher chances at 60-80% along the north Oregon coast including
KAST. Any moderate to heavy rain today may also lead to brief VIS
reductions to IFR/MVFR. Showers will mostly dissipate by 10z Fri.

Easterly winds along the coast will turn more southerly with gusts
up to 20-25 kt from 20z Thu through 00z Fri. Otherwise, winds remain
light less than 6 kts and variable elsewhere except for breezy
easterly winds through the Columbia River Gorge with gusts up to 20
kt near KTTD through 21-23z Thu.

KPDX AND APPROACHES...VFR with mid to high level clouds and
occasional rain showers through 10z Fri. Easterly winds around 5 kt
or less turning southerly this evening. -03

&&

.MARINE...As of early Thursday morning, a front associated with
a low pressure system centered offshore of northern California
is bringing east-southeasterly winds 10-15 kt with gusts up to
20 kt across the waters. Later this afternoon, the low will
deepen and swing another front through the waters. This will
return breezy southerly winds 15-25 kt with gusts up to 30 kt.
Seas build towards 10-13 feet at 12-15 seconds by early Thursday
afternoon for all waters. Isolated gale-force gusts up to 40 kt
are possible Thursday afternoon/evening, mainly south of Cape
Falcon and beyond 20 NM off the coast. This area will also have
a 50-70% chance for seas building towards 13-15 ft for the same
time frame. Therefore, the current Small Craft Advisory for all
marine zones remain in effect through at least 7 AM Friday. Seas
gradually subside to 8-9 ft at 13 seconds Friday afternoon as
the low pressure system weakens and progresses southward.

Another frontal system will swing through British Columbia and
far northwest Washington Friday afternoon, maintaining
relative breezy southwesterly winds over our coastal waters.
There is a 30-50% chance for southwesterly winds with frequent
gusts of 21 kt or stronger across the waters north of Cape
Falcon including the Columbia River Bar by late Friday afternoon
and evening. South of Cape Falcon, these chances drop to
15-30%. Winds ease on Saturday in between systems.       -10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 7 AM PST Friday for PZZ210-251>253.

     Small Craft Advisory until 1 PM PST Friday for PZZ271>273.
&&

$$

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